Indoor Environmental Technologies (IET) was retained by the builder to determine the cause of excessive sweating of HVAC ducting equipment and components in a $3 million home. The residence had been occupied less than one month and was showing elevated humidity conditions in the second story of the home. Mold growth was starting in both home and attic. IET performed thermal imaging, analysis of data-logged temperature/humidity conditions, and analysis of pressure differential between the inside of the home and outdoors.

Results of inspection: Energy-efficient measures taken during construction had contributed to the development of 'cold attic syndrome,' where air conditioning ducts in a ventilated but cool attic in a hot/humid climate are prone to excessive condensation. Various building design features had contributed to significant negative pressure and infiltration of exterior humid air into the occupied space, resulting in excessive humidity in the home and in interior wall cavities.

Recommendations for correction: Seal attic from outside air. Install dehumidifier in attic to control humidity. Install separate ventilation air dehumidifier to ensure positive pressure in the occupied space and help control interior humidity.

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